1. Field of the Invention
This invention relates to a molding die for injection molding resin materials or the like. More particularly, this invention relates to a cassette-type molding die including a die plate unit having one or more cassette fitting bores and a cassette die unit capable of being detachably inserted into the fitting bores of the die plate unit.
2. Description of the Prior Art
In the field of resin molding, there has been cherished the idea such that only a core and a cavity which are essential elements in a molding die system are designed to be separated from a molding die frame and detachably incorporated in the molding die frame like a cassette Specifically, from a consideration of a current tendency to produce various kinds of molded products in a small quantity, such a conventional molding die system has entailed problems such as difficulty in changing the molding die with another molding die. Furthermore, the work for designing and producing the desired molding die requires much time and labor and is disadvantageous from the standpoint of cost.
In order to eliminate the problems described above, there have been proposed various molding dies of a cassette type.
In Japanese Patent Application Public Disclosure SHO No. 57-6738, a technical idea of fitting an exchangeable cassette die between a stationary die plate and a movable die plate is disclosed. Japanese Patent Publication Gazette SHO No. 61-53213 and Japanese Patent Application Public Disclosure SHO No. 60-116420 each describe a molding die structure in which stationary and movable die plates are provided in their opposed parting face portions with fitting bores for allowing cassette die halves to be inserted therein from the fronts of the respective parting faces. Also, Japanese Patent Application Public Disclosure SHO No. 59-174331 teaches a molding die device in which a separate cassette die can be detachably inserted into a molding die unit through the upper opening formed in the molding die unit.
However, in order to fit the cassette die halves into the fitting bores formed in the stationary and movable die plates from the fronts of the parting faces of the die plates as taught by the aforementioned Japanese Patent Publication Gazette SHO No. 61-53213 and Japanese Patent Application Public Disclosure SHO No. 60-116420, the die plates must be opened wider compared with the case of normal mold opening. Therefore, the work for exchanging the cassette die consumes much time and labor. Specifically, in case that a required molded product is large in height, it is necessary to open the die plates more widely. Thus, these facts prove to counterbalance the advantage of the cassette-type molding die.
The aforementioned shortcoming of the conventional cassette-type molding die will be remedied by adopting a molding die structure as proposed by Japanese Patent Application Public Disclosure SHO No. 59-174331. However, in this prior art structure, when one of the cassette die halves is fitted in the movable die plate, it is difficult to insert the separate movable cassette plate, ejector plate ejector pins in the movable die plate at a time, whereas the prior art makes no mention of means for effecting the work of fitting the separate elements into the die plate at a time.